The present invention relates to an improved technique for producing an acrylonitrile dimerization catalyst composed of a ruthenium complex on an organic polymer support.
Commonly assigned U.S. Ser. No. 291,708, now U.S. Pat. No. 4,422,980, the disclosure of which is incorporated herein by reference, discloses certain acrylonitrile dimerization catalysts which comprise a polymeric material having a ruthenium complex bonded thereto. In general, these catalysts are made by mixing the polymer support and an excess of the ruthenium complex together for a suitable period of time. In accordance with the present invention, it has now been discovered that the ability of the catalyst to produce the desired dimerization product is significantly enhanced if the ruthenium complex is added to the polymer support over an extended period of time as opposed to all at once.
Thus, the present invention provides a process for producing catalysts comprising a polymer support having a ruthenium complex bonded thereto, the polymer support comprising an organic polymer backbone having trivalent pendant atoms selected from P, As, Sb, Bi and N covalently bonded thereto and randomly distributed in the polymer, the ruthenium complex capable of catalyzing the dimerization of acrylonitrile to adiponitrile and/or 1,4-dicyanobutenes and comprising Ru and at least two homogeneous ligands having at least four ligating bonds bonding to the Ru, the Ru in each ruthenium complex datively bonding to a pendant atom in the polymer support, the Ru/pendant atom ratio in the catalyst being at least 0.001, the complex having on the average no more than one homogeneous phosphine ligand per atom of ruthenium, the process comprising adding the ruthenium complex to the polymer support over a period of time of at least 3 hours.